WILLISTON — A manufacturer of renewable energy equipment has found a formula to get its employees to save energy: a $6,000 annual bonus, offset with a carbon tax.

David Blittersdorf, CEO at AllEarth Renewables, said he has long tried to walk the talk as a maker of renewable energy equipment. In 2011, he proposed a car tax on his 31 employees, but some balked and helped brainstorm another solution.

The result is REWIRE, an incentive program in which employees are offered the annual bonus, then taxed against it for using fossil fuel energy for driving, heating or powering their homes.

“Basically, you put a pot of money there, you subtract all the carbon-intensive stuff and they get the balance,” Blittersdorf said. “The less they do (in emitting carbon), the more money they have.”

All energy use is converted into kilowatt-hours, which are taxed at 15 cents each. The energy in a gallon of gasoline equates to about 37 kilowatt-hours, said Andrew Savage, the company’s chief strategy officer. A 20-mile round-trip commute in a car getting 20 mpg costs an AllEarth employee about $5.55 in REWIRE tax, plus the regular price of gas.

The result has been a lot more carpooling, bus-taking and bike-riding — and even thinking twice about weekend trips out of town. It all shows up on the annual odometer check by the Human Resources Department.

Chief Operating Officer Doug Goldsmith has bested the other employees the past two years, earning $4,400 of the bonus in 2012 and $4,816 in 2013. He bikes to work, heats his home with wood pellets and gets his electricity from solar power.

Some employees end up with no bonus, but big carbon emitters don’t end up owing the company money, Savage said.

As a result of the program, Savage said, auto usage in the company dropped 7 percent from 2012 to 2013 and electric usage decreased by 21 percent. Heating was up a bit, he said, because of last year’s bitterly cold winter.

George Twigg, public affairs director at the Burlington-based Vermont Energy Investment Corp., which consults nationally on energy conservation and renewables, praised the program, saying the annual bonus offset by a carbon tax is “sort of a carrot in the shape of a stick.”

“It’s definitely a different approach in terms of the psychology of motivating action,” Twigg said.

Twigg said his firm and others subsidize individual employee actions like the purchase of a hybrid car or an energy-efficient appliance. But he said he wasn’t aware of another program that had AllEarth’s carbon tax.

A $6,000 benefit for 31 employees works out to $186,000, Blittersdorf said, but employees have been able to collect only about half of that so far.

“That is a small thing compared to our total payroll,” he said. “If you look at it in all the scheme of things, I think it’s a huge positive investment” for the company and the planet.

As for Goldsmith, he said he was happily doubtful he would place first for energy savings a third year in a row.